Hollow Cathode Active Material for Power and Cycle Stability
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Solution Overview
Problem
Existing nickel-containing positive electrode active materials, such as lithium nickel cobalt manganese oxide ternary materials, face a trade-off between improved power performance and cycling stability, with enhancements in one often leading to deterioration in the other.
Innovation Solution
A positive electrode active material with hollow secondary particles and specific elements M and A distributed at grain boundaries, along with controlled residual alkali content, to enhance bonding strength, ion transport, and reduce side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If nickel-containing positive electrode active materials are used to improve power performance, then power performance is improved, but cycling performance deteriorates
Solution Approach 1:
The patent applies local quality by creating hollow secondary particles with specific structural characteristics. The hollow structure is formed by controlling the aggregation of primary particles, creating a unique morphology where the interior is hollow while the exterior maintains structural integrity. This local structural modification improves power performance by reducing ion diffusion paths while the overall hollow structure enhances cycling stability by reducing mechanical stress during charge-discharge cycles.
Solution Approach 2:
The patent employs composite materials by combining multiple elements (Li, Ni, Co, Mn, A, M, B) in a controlled composition within the hollow secondary particle structure. The specific element composition and their strategic distribution create a composite material system where each element contributes specific properties: Ni provides high capacity, Co and Mn enhance stability, while elements A, M, and B are strategically positioned to stabilize the crystal structure and improve bonding strength, achieving both high power performance and cycling stability.
2Stability of the object's composition
If element M is distributed in the bulk-phase part of primary particles, then crystal structure is stabilized, but ion transport rate at grain boundaries is reduced
Solution Approach 1:
The patent applies local quality by strategically distributing element M at the grain boundaries rather than uniformly throughout the bulk-phase. This localized positioning at grain boundaries specifically targets the regions where ion transport occurs, enhancing ion transport rate without compromising the overall crystal structure stability. The grain boundary localization allows element M to fulfill dual functions: stabilizing the crystal structure while simultaneously facilitating faster ion transport pathways.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves both power performance and cycling stability by stabilizing the crystal structure, reducing internal resistance, and accelerating ion transmission while minimizing cracking and side reactions.
Implementation Method 1
the hollow structure of the hollow secondary particles is conducive to reducing the internal resistance of the particles, shortening the lithium ion diffusion path, and accelerating the transmission of ions inside the particles
Implementation Method 2
it is beneficial to stabilize the crystal structure of the primary particles, improve the bonding strength between the primary particles and reduce the cracking and breaking of the hollow secondary particles during cycling
Implementation Method 3
the element M mainly distributed at the grain boundaries can better coordinate with residual alkali of the positive electrode active material, which is conducive to strengthening the bonding strength of element M to the grain boundaries
Data Source
AI summary
A positive electrode active material and a preparation method therefor, a positive electrode sheet, a secondary battery, and an electric device, wherein the positive electrode active material comprises hollow secondary particles, the hollow secondary particles comprising LiaNixCoyMnzAqMpOb, 0.25≤a≤1.2, 1.8≤b≤2, 0.3≤x≤0.6, 0≤y≤0.4, 0<z≤0.4, 0≤q≤0.02, and 0<p≤0.02, the atomic percentage of element M at grain boundaries being greater than or equal to the atomic percentage of element M in bulk phase parts of primary particles, and element A being distributed in the hollow secondary particles in the form of bulk phase doping. The positive electrode active material comprises the hollow secondary particles, element M is mainly distributed at the grain boundary of the hollow secondary particles, and element A can be optionally doped, thereby keeping good cycle performance while effectively improving the power performance.